[Mindcore]

Hi, I'm a newb. My first post here.

I've built a CNC mill, a combo of MDF and extruded aluminum. Running on v-groove bearings. Table is 3' wide X 6' long, with a 6" Z axis.

It's home built, so it won't be perfect, but seems very smooth so far.

I'll be cutting hardwood and some aluminum.

I was looking at the hobbyCNC kits, and after emailing them got the response that their systems are not appropriate for my machine. Now I'm lost because that means I need to do a whoooollleee lot more learning, or come to you guys that know this stuff and ask if you have any recommendations for an all in one kit.

I've been reading the forums for a while now, and I know you guys are passionate about it, but frankly I just want to use it. Knowing which model # gives me that extra 1% is more then I need or want to know.

So, with that any ideas? have I given enough information?

Thanks

[pfred2]

I checked out that hobycnc site and while their kit may not have been optimal for you I cannot imagine it would not have worked at all.

Here are some plug it in and go setups they most likely won't turn you away from buying:
http://www.super-tech.com/root/itm.a...m-emc-geckopwr

Now if you want to make a more informed decision reading this may help:

http://www.cnczone.com/forums/attach...4&d=1107010394

TANFL you get out what you put in.

[Mindcore]

Thanks for the reply. The super-tech link is sum $2000.00 more then the hobbyCNC, there in lies the problem I guess?

[judleroy]

How about something like this? http://www.kelinginc.net/CNCNEMA23Package.html

[pfred2]

I tried to do a little research about just who, or what Keling is and never really came up with any satisfactory answers. For me the real question isn't so much how but what?

This left me a bit sour:
http://www.cnczone.com/forums/showthread.php?t=31438

We all have to decide for ourselves what the threshold of our personal comfort levels are. After seeing what I have I am still not feeling too warm or fuzzy about Keling.

I will keep them in mind the next time I need a hot water heater.
http://www.importgenius.com/shipment...nology-co.html

TANSTAAFL

[James Newton]

I'm not sure how anyone can recommend a driver without knowing what stepper motors you plan to use...

And I don't think you can pick the stepper motors until you know how much torque you need to supply and how fast you want to traverse...

Or did I miss something there?

[Mindcore]

I think you did. I'm looking for an all in one kit. Drivers and steppers that would be suitable for a machine my size that is capable of cutting hardwood and aluminum.

I'd like a decent rate, but I'm not a shop. It's a hobby I'm not charging anyone by the hour. So it doesn't need to be the fastest thing out there, but I'd like it to be faster then by hand

[MrWild]

What kind of lead screws? How many start? Thread pitch per inch? With a machine that large, you want faster rapids than a Hobby CNC kit will give. Their drives don't have enough volts. Keiling sells kits with geckos, motors and matched power supplies. Buy the G540, 381/387 steppers, and 48v power supply for the most pain free bang fr the buck kit. The parts can be bought from many suppliers besides Keiling, but the package is sound.

With the BOB an integral part of the driver set up, including a charge pump circuit, PWM motor control, 2 x outputs, 4 x inputs, and Estop, the wiring is much easier using a G540. About the best bang for the buck.

If you want faster rapids, three G203s, a 70v power supply and 600+ozin motors with five start lead screws would be a nicer but also a more involved and expensive choice. Spending the huge bucks for one of the kits shown with over $2,000 price tags is silliness. IMO

Just because one person is a little sour over an unrelated product from years ago isn't a reason to pass by a supplier. Keiling has stood by it's products and refunded/replaced with no hassle when needed. I've had nothing but good results so far with my purchases from Keiling.

[Mindcore]

Thanks for the reply. I'm using standard threaded rod at the moment, but may change after to lead screws. I don't recall the TPI at the moment, I'm thinking 14 or so?

Not sure what how many starts means.. like I said, I am really new.

I'm going to take a look at your suggestions now. thanks

[MrWild]

Lead screws come in single start, double start and five start. This means there can be a single thread (single start) that will move the nut one thread per full turn. double start or two start has two screw threads that overlap. This will move the nut two threads per full turn of the lead screw. Five start has five screw threads that overlap.

If you have single start 1/2" -10. (ten threads per inch) it will take ten turns of the lead screw to move an inch. With a two start 1/2"-10, it will move an inch in just FIVE turns. A five start moves a whole inch in just one turn.

This is important to know because stepper motors lose power the faster they spin. People have had huge speed improvements by going with multi start lead screws using the same motors because the motor has the power at low rpms to turn the screw EVEN WITH MORE TRAVEL PER REVOLUTION.

Large and/or more powerful steppers can actually have less power at higher rpm than smaller weaker ones. This is due to the size of the windings and how fast electrical current can fill the coils. So you want something that matches the entire system.

With 1/2-13 or 3/8-16, you want a motor that has more power at higher rpms and that means a smaller stepper than those monster kits for over $2k. My suggestion for a set up would be 1/2-10 two start lead screws, DumpsterCNC anti-backlash lead nuts, Gecko G540, Keiling 381/387ozin steppers (they match the G540 very well) and a 48v 7.2A power supply. This will give fair rapids for your large machine without breaking the bank. Trust me on this, I am Mr Cheap and tried to go the as inexpensive as I could route. This winds up costing much more in the end due to buying things twice or three times. If your router were 1/2 the size, you'd be okay with a cheaper set of motors, weaker power supply, and junk Chinese drives from ebay. With a good sized router like yours, weak will work, but the speed will be teeth pulling slow.

The great thing about a Gecko drive is that it holds a much better resale value if you decide you want even more power/speed and move up from a G540 to three G203s and a BOB with higher voltage power supply. Just like racing speed costs money and you don't put a lawn mower engine in a street car expecting to move faster than a snails pace. Cheap drives/motors and a large router is painful.

If you need to save bucks, look into EMC2 (free versus Mach3 ($150) for your control program. The more I play with EMC2, the more I like it.

[James Newton]

Yeah, all in one kit, I understood that. What I don't get is how you can know what size motors you need if you haven't measured the torque required to turn the lead screws on your machine...

[jschmitt]

you will not like the rapids of a 14tpi screw on a 3' x 6' machine. Also you need to consider screw whip on the 6' axis. You would be wise to consider either a belt setup or rack and pinion. I had screw whip limiting my rapids on a 48" axis with 10 tpi.

[pfred2]

They want an all in one kit and they don't want to figure anything out so what don't you get? They're obviously looking for the easiest solution for themselves.

I posted a link to the CNCMechanics resource on this site second post in the thread and that fell on deaf ears.

Now all that remains is can anyone recommend a good consultant to the original poster? Or are we all expected to work for free?

[Mindcore]

Some of you guys slay me.

To the ones that helped with recommendations, thank you. It's given me a step in the right direction.

To the CNC experts that are so perturbed by my questions, spare me. Post somewhere else. I didn't ask for someone to come over to my house and build it for me. I went in a direction that I thought was right and found out it was perhaps wrong. I came here looking for advice.

I said what I was using, and that I wanted an all in one kit. Perhaps I should go fabricate my own capacitors and wind my own motors.. oh wait, I guess I did that when I built 3 of my own wind turbines.

I'm not a moron, this is a tool for me and I want it to be as simple as it can be.

You guys take this seriously, I get that. Why did you think I came here to experts for advice.

I've spent more years then I can count dooling out "Free" advice on the many topics I do know inside and out...and backwards.

Jschmitt, thank you, I came to the same conclusions myself today regarding whip, and have been thinking of options to overcome it, as well based on some of my math, I agree as well I'm not going to like the speed with my current screw. My current design will however make it very easy to upgrade once I get it running and a handle on what it does.

[RomanLini]

There's nothing to gain from having an attitude Mindcore. Nobody in the thread has attacked or abused you, it looks like everyone has tried to help you. Getting huffy because all the help is "not perfectly what you wanted" is a bit silly.

Your first post mentioned the hobbycnc kits and the question of whether they were suitable for your machine. We haven't seen your machine. Other people who wanted to help you have asked you for more info.

Maybe you could post some photo's of the machine you have built, which will be a huge help to people who can look at the photos and quickly determine the size motors and drivers etc that you need, or they can offer options like a cheaper setup that will work OK or a more expensive setup that will work very well.

[pfred2]

I have witnessed a behavior with some in the DIY CNC crowd where they appear to closely guard information about their machines. I'm sure their motives vary. The frustrating end result rarely does though.

This is what we presently know about the mysterious X1 stealth CNC machine:
Table is 3' wide X 6' long, with a 6" Z axis.
Wood, and some aluminum are the target stock materials.
I don't recall the TPI at the moment, I'm thinking 14 or so?

Based on this limited flow of information Jschmitt appears to have convinced Mindcore that a lead screw upgrade may be in order.

I smelled out the cloak and dagger aspect of this particular user early on and in my first reply to them gave them a link to a resource that they could use to plug in all of their numbers and come up with all the answers they could hope for. Why they didn't scuttle back to Area 51 with the document and this thread is still going is beyond me!

But hey, that's what we all know and love about the Zone right?

http://www.jumpstation.ca/recroom/co.../argument.html

Roman you may enjoy an old SLAm I made (its a 7026):
http://img683.imageshack.us/img683/6498/stepproto1.jpg

I'm digging these now though:
http://img580.imageshack.us/img580/8...hqnoflash1.jpg

This is a thread hijacking! Ha-ha! It's still April right?

[Mindcore]

First I'll admit I was in an unrelated bad mood yesterday.

That aside, it's painfully obvious that some have that oh so typical "elitest" attitude you see so rampant on forums these days.

There is no cloak and dagger. I'm a week into my build, I'm roughing it and learning as much as I can in a very short amount of time, while still trying to do my job, family etc.

My machine is no mystery, I didn't build off plans, just a few pics I've seen on the net, and I've had fun doing it.

Here's a pic, though the Z axis has changed dramatically as I wasn't happy with the one shown.

Again, I'm very thankful for the advice, and the amount of knowledge I've gained on this forum.

I read your link, it was very informative, but this is a forum, an open exchange of information, excuse me for continuing on with my thread.

I'll take your link do the math and run to my little cave then

[pfred2]

I'm sure that there are plenty of people willing to go to great lengths to help you out here but it is a show of good faith to meet them half way.

I cannot tell from the picture if your long table X axis is driven by a single, or a dual lead screw. There is a complicated cabling system some employ to keep their wide axis square when they drive with a central single lead. Maybe you have that installed already too? Again, I cannot tell from the picture. If not, maybe you should look into it?

Your machine looks a lot like this one to me:
http://buildyourcnc.com/DesktopCNCMa...blueChick.aspx

I prefer the older way he used to do his linear bearings. Then one can use plain skate bearings and not those expensive V groove ones. It does look from your picture like you are trying to use plain skate bearings with the raised guide edge reversed, as a shoulder. I'd be interested in seeing how that works out for you. Have you thrown a handful of router chips at it to see how it works? Because even if you don't I'm sure Mr. Porter Cable will!

I hope you use a great vacuum system to clear debris from laying where your bearings roll.

You say you've seen some examples on the Internet, have you seen these?

http://www.mechmate.com/

http://www.joescnc.com/themachines-hybrid.php

There are lots of others but those two strike me as being some of the more mechanically sound ones out there. Not knowing more I think you may have taken a basic moving gantry design and scaled it up past where it works completely reliably. But who knows, maybe you'll get lucky? Or maybe it'll be the rack for you!

http://people.csail.mit.edu/paulfitz...sh/script.html

[Mindcore]

I'll gladly meet more than half way

That picture was taken prior to the installation of the lead screws. I was concerned about both sides of the gantry staying inline with each other, so I have since run two lead screws ( one on each side ) which links to a chain drive and sprocket centered on the bottom of the table.

I've ran it back and forth with a power drill to see if it's staying in line, and many measurements tell me it's not drifting out at all.

I started out with plain skate bearings but wasn't happy with the play in them, especially with the size, so I have have v-bearings on order which should be here tomorrow hopefully and I will get those running. My method of using the skate bearings left too much play, and caused excessive drag at the same time.

My machine does look a lot like that link, that's probably the picture I had in my head when I built this thing. I know I appear to be a little crazy, but I basically just started building it one Saturday with out following any plans and what you see in the pic was what I had done by Sunday afternoon. I didn't put a whole lot of thought into it, but I'm impulsive that way. I do get the basic principles of what it does, and how it does it, so I went with that.

I haven't thrown anything at it yet, but I expect the redesign with the v-bearings will eliminate a lot of the potential issues. My new X-axis assembly has the brackets built in to clamp a central shopvac system up to it. It works fine for my other tools, so I'm hoping it will keep up with this beast. I guess I'll find out.

I hadn't seen the last two links you posted, and they sure look more sound than mine. Since that pic was taken I've changed a lot of components out to aluminum so my stability has increased quite a bit. I'll take some more photos tonight and post them up.

It may just wind up being a rack, but then we're back to my original question...

What stepper motors should I use to pull my arms off?

[James Newton]

Dude, I'm really sorry if I gave the impression of being either elitist or taking this **** too seriously. I was truly trying to help.

But there is no way we can answer your question without knowing how much torque is required to turn the lead-screw.

Why? Because Stepper Motors are rated by how much torque they can HOLD, and some fraction of that is how much torque they can PULL. In general you can guess how much they can pull by the number of WATTs (volts times amps) they will put out.

Look, it isn't all that hard: Just buy a torque wrench, or hang a rod 1 foot long off the end of the lead screw, then add weight until it drops, turning the screw. That will give you the foot pounds (actually pounds per foot) of torque which you can convert to in-oz using the converter at:
http://techref.massmind.org/techref/torque.htm

Now you know how much torque you need to supply. The next trick is the different between pull and hold. You can make a really rough guess by just dividing the motors holding torque by about 5. I think... anyone? Actually it depends on the speed.

Someone (much smarter than I *cough* Maris *cough*) said the magic formula is:

Watts = in-oz * RPM / 1351

If you measure 1 pound at 1 foot is required to turn the lead screw then that is 192 in-oz. If you want to turn that at 1000 RPM then you need about 150 watts. So a 50 volt, 3 amp motor would do it. Or a 15 volt 30 amp motor. Or any combination that comes up to 150 watts.

Hopefully, yours will turn easier than that.

Someone check my method and math please? I'm not an expert, I don't do this for a living, I could easily be wrong...

I'm just trying to be helpful.